martin



T. G. MARTIN.

PARTY LINE SELECTIVE SIGNALING SYSTEM.

APPLICATION HUD NOVZQ. 1909 1 ,306,4:94:. Patented June 10, 1919.

2 SHEETS SHEET I.

(Uiinepjsefl M72602;

a .MW. (606 m mm 1' 1, I

G. MARTIN.

PARTY LINE SELECHVE SIGNALING SYSTEM.

APPLICATION FILED NOV. 29, I909.

-provement in UNITED STATE? PATENT OFFICE.

armor o. MARTIN, or CHICAGO,

comramr,

ILLINOIS, ASSIGNOB 'I'O AU'IOHL'I'IC ELECTRIC OF CHICAGO, ILLINOIS, A CORPORATION OF ILIJNOIS.

PARTY-LINE SELECTIVE SIGNALING SYSTEM.

Application filed November 29, 1909. Serial To all whom it may concern:

Be it known that I, TALBOT G. MARTIN, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful Im- Party-Line Selective Signaling Systems, of which the following is a specification.

My invention relates to telephone exchange systems of that kind in which party line subscribers are rovided with means for calling automatical y, and in which provi sion is made whereby, when the call is from one subscriber to another on the same line, a connector is adapted to callingsubscriber to seize the calling line, and to then signal the called subscriber thereon, a call of this kind being sometimes referred to as a reverting call, as will hereinafter more fully appear.

Objects of my invention are to provide a connector having provisions for calling back on the calling line, and for selecting the desired or necessary frequency of ringing current for signaling the called subscriber, whereby the calling subscriber may not only automatically call another subscriber on the same line, but may also then selectively signal that subscriber; to provide a system in which the automatic switches are controlled over the two sides of the calling line in series, and in which a party-line subscriber may call and signal another subscriber on the same line; to provide a system in whic the automatic switches are controlled over the two sides of the calling line in series, and in which means are provi ed for enabling the calling subscriber to select the frequency of ringing current necessary for signaling a particular subscriber on the party-line; to provide a system in which provision is made for interrupting the signaling current on the part -line when one subscriber calls another on t e same line, whereby the calling sub scriber may release; and to provide certain details and features of im rovement tending to increase the general ciency and serviccahility of a telephonic exchange system of this particular character.

To the foregoing and other useful ends my invention consists in matters hereinafter set forth and claimed.

In the. accompanyin drawings, which illustrate a system embo ying the principles of my invention, Figure 1 shows'the electrical circuits and mechanical parts of the Specification of Letters Patent.

Patented June 10, 1919.

master switch. In Fig. 2 the telephones A and A of said system are shown connected.

' The system shown represents a four-party line group connected to a line switch group with trunking facilities through a first selector group and a connector switch group to the bank terminals equipped with ringing current.

For the purpose of explaining this invention a single four-party line with its line switch, a trunk to the first selector and a trunk to the frequency connector switch will be considered. For operating and for talking purposes a central source of current B is rovided having its positive terminal preferably grounded. However, the line switch group may be considered separately from the main central office, in which case it will be equipped with a source of operating current separate from the main or trunking oflice. The switching apparatus which is shown, and through which the party-line subscriber is connected to the ringing current, and to the source of current for talking purposes, possesses many characteristic features which are well known. Comprised in said switching apparatus is a subscribers line switch C, which is of an improved and highly eiiicient type. The said switch C is an improvemen upon that disclosed in English Patent No. 26,301 of 1906, for telephone systems and apparatus. It is designed to operate automatically when the subscriber at the allotted substation takes his receiver off the hook to seize an idle trunk line leading to the next switch, preferably to the first selector. The switch D with which the switch C is shown connected is a selector switch of the general type disclosed in United States Letters Patout No. 815,321, granted March 13, 1906, to Keith, Erickson and Erickson, and comprises certain new features adapting it to a two-Wire automatic telephone system. The switch E with which the selector D is shown connected throu h its second level is a connector switch 0 the general ty e disclosed in United States Letters Patent 0. 815,176, granted March 13, 1906, to Keith, Erickson and Erickson, and comprises certain new features adapting it to the special purpose of this invention, and to a two-wire automatic telephone exchange system. The switch F is a master switch for controlling the line switch C and all other line switches of the same group. The said line. selector and connector switches are adapted to be operated from the calling substation by the calling device. The line switch performs a nonnumerical trunking operation, while the selector and connector operate in accordance with digits of the called number. The central exchange is further provided with a central source of ringing current of four different frequencies f, f", f and F", each independent of the other, and a source of busy signaling current S. The switch C is allotted to the party-line P, to which partyline the substations A, A and A are connected. The substations A, A and A may be of any suitable or approved type, but their respective ringers are adapted to respond to ringing current of a particular frequency, and not to current of the same frequency required to operate any of the other ringers on the same line. For example, the ringer at substation A will only respond to ringing current from the generator f, the current supplied by the generator I will actuate only the bell at substation A, while the substation A may be signaled only by the generator F. In former automatic party-line systems employing selective signaling it has been the usual custom for a subscriber to call another subscriber on his own line by calling the same number, by which that subscriber would be called from a substation on some other line. In my improved system, however, a subscriber may signal another subscriber on his own line by callin a special number, different from that by which said called subscriber is called from a substation on another line. With the apparatus arranged as shown in Fig. 1, this special number consists of only two digits.

The substation A (Fig. 2) comprises the receiver 2, switch book 3, induction coil 4 which consists of the primary winding 5 and secondary winding 6, transmitter 7 condenser 8, the frequency ringer 9, push button 10 and resistance coil 11. In addition to the above-mentioned parts there is provided an impulse wheel 12 which has the usual teeth adapted to separate the springs 13 and 14. The switch hook has a radiating cam which presses down on the spring 15 when the hook is down, separates the springs 15 and 16 and presses the springs 15 and 17 into engagement. The switch hook is pivotally secured to the frame of the calling device (not shown) and is forced up, when the receiver is off the hook, by a spring (not shown). The dial (not shown) is rigidly connected to the impulse whee The movement of the dial and, therefore, of the impulse wheel provides the subscriber with means for separating the im ulse springs 13 and 14 and selecting the sustation desired by operating the automatic switches at the central oflice. The upward movement of the switch hook opens the circuit of the condensmand ringer in series, previously bridged across the line, by allowing the spring 15 to pass out of engagement with the spring 17. When the spring 15 passes into engagement with the spring 16 the transmitter 7 and primary winding 5 of the induction coil 4 are bridged across the line, given a common battery talking circuit. The push button 10 normally short-circuits the resistance 11. When the push button is operated the short-circuit is taken 011' the 'resistance coil, thus enabling the subscriber to ring another substation on his line after he has connected with the bank terminals of the connector E at the central station.

The trunking switch C is a modified form of the trunking switch disclosed in British Letters Patent No. 26,301 of 1906, and in the Western E lectviciwn of Chicago, Illinois, of January 25, 1908. The trunking switch C comprises the plunger 92 (Fig. 1) ivotally mounted on the plunger arm 18. dpon the end of the plunger arm 18 there is mounted a thumb screw 19 which is attached to the spiral spring 20, which latter is rigidly secured to a bracket (not shown). The thumb screw and the spiral spring arrangement admit of a proper tensioning adjustment of the plunger arm. Above the plunger arm there is a set screw 21 mounted on the bracket for limiting the backward motion of the plunger arm. The magnet 22 of the switch C is divided into two sections 23 and 24. The section 23 comprises two windmgs, a trip magnet winding 25 and a bridgecut-ofi winding 26. The end 24 comprises two line relay windings 27 and 28 one winding serving a double purpose. liloth windm on the end 24 control the armature 29.

en the armature 29 is attracted the spring 30 is pressed into contact with the spring 31. The bridge-cut-olf armature 32, when attracted, shifts the springs 33 and 34 out of engagement with the springs 35 and 31. The trip magnet winding 25, when energiaed, attracts the plunger arm 18 and the bridge-cut-ofi' armature 32. The windin 27 is in series with the winding 25 and hot are energized simultaneously, thus holding the armature 29 in an attracted position and the springs 31 and 30 in contact until the battery cut-off relay 55 is operated. The bridge-cut-ofl' winding 26, besides attracting the armature 32 from normal position, acts as a holding coil to hold the plunger arm in an attracted position, but cannot independently attract the plunger arm from the stop 21 on account of pulling against the tension of the spiral spring 20. l

The master switch F (Figs. 1 and 2) which controls the plunger shaft 39 of the line switches may be of the general type disclosed in the above-mentioned Western. Electrician of January 25, 1908, and in the American Telephone Journal of Chicago, Illinois, of June 6, 1908. The said master switch F comprises the usual motor magnet 36 adapted to operate which is in turn linked to the plunger shaft 39 by the pivoted link 40. The link 40 translates the circular motion of the ratchet wheel to the plunger shaft 39, giving it a rotary reciprocating motion.

The master switch bank is shown at O and comprises the individual segments a and the common segment 42. The wiper 41 is adapted to maintain some one of the individual segments a in electrical contact with the common segment 42. The motor magnet relay 43 is, as usual, arranged to close an energizing circuit through the motor magnet 36. Rigidly secured to the plunger shaft 39 is the cam 44 provided with circular openings 45 corresponding to the individual se cuts a in the master switch bank 0. T e pin 46 secured to the arm 47, the latter being pivoted at the point 48, is fitted to engage the openings 45 when the plunger shaft 39 is rotated. The spring 49 holds the pin 46 against the cam 44 through the bushing 50 and completes a circuit through the motor magnet 36 by engaging the spring 51. The auxiliary relay 52 con trols the circuit through the relay 43. The motor magnet relay 43, when energized, attracts its armature, draws the pin 46 out of locking cngagement with the cam 44 and closes the motor magnet circuit. The interrupter springs 139 and 140 on the armature of the motor magnet cause it to rapidly energize and deenergize. In multiple with the motor magnet is the relay 55 which controls the supply of direct current and busy sifgnaling current to the line relay windings o the trip-in windings of the cup of line switches to which the switch belongs.

The first selector switch shown at D is of the general type described in United States Letters Patent No. 815,321, previously mentioned, and, as shown, is modified to adapt it to operate in connection with a twowire common battery system. Among other detail it embodies the following features: The switch shaft (not shown) carries the line wipers 56 and 57, together with the private wiper 58. The side switch is well known an comprises the wipers 59. 60, 61 and 62. The side switch is under the control of the private magnet 64, and when said side switch is in normal or first position the Wipers 59, 60, 61 and 62 occupy the contact points 63, 65, 66 and 67, respectively; when in second position the wipers rest on the contact points 69, 70. 71 and 72, respectively; and when in the third position the contact points 74, 75, 76 and 77 are engaged b their respective wipers. The windin of the usual vertical and rotary line re ays are. in this case.

combined into one double-wound relay 79.

Through the medium of this double-wound lino relay, and

the ratchet wheel 37 while the side switch is in first position, the subscriber controls the vertical magnet 81, which operates to raise the switch shaft and wipers 56, 57 and 58 vertically. The line relay 79 also controls the private magnet relay 80, which latter in turn controls the private magnet 64. \Vhilc the side switch is in second position the rotary magnet 82 which operates to rotate the shaft and shaft wipers 56, 57 and 58 in a rotary direction is energized. The release magnet 83 provides means for restoring the switch to normal position. Upon the switch shaft. is mounted the arm 84 which, when the shaft is raised one or more steps, permits the spring 85 to engage the contact point 86. whereby the release magnet 83 is connected to the battery lead. The line relay 79 con trols the release relay 87 which is provided for closing the energizing circuit of the release magnet 83 after the switch is operated. Furthermore the release relay 17, upon energizing, provides an energizing circuit for the bridge-cut-ofi winding 26 of the line switch C to maintain the switch in its operated position. The relays 80 and 87 are slow-acting relays-that is, they are so provided with a copper shield that when energized. and when the energizing circuit is broken, the said relays do not. instantly return to normal.

The frequency connector switch E is a modified form of the usual connector switch modified to adapt it to operate in a twowire common battery system. The connector 1 00 switch shaft (not shown) carries only two wipers 88 and 89 and has rotary motion only. The vertical magnet and armature usual to a connector switch are omitted. The sidc switch has only two positions. whereas in the usual connector it has three positions. The side switch wipers 90 and 91. in the first posit-ion, engage the contact points 93 and 94, respectively, and in the second position the contact points 96 and 97. The frequency connector is also controlled by the calling subscriber through the medium of the relays 99 and 100. The line relay 100 directly controls the rotary magnet 102 which gives to the shaft and .haft wipers 88 and 89 a rotary motion. As usual, the slow-acting pri vate magnet relay 101 controls the private magnet 103, which controls the side switch and side switch wipers 90 and 91. The relay 101 being in series with the rotary magnet 102 is energized when the rotary nmgnct 102 is energized, but being a slowacting relay it does not release its armature as the rotary magnet does. but attracts its nrmaturc all the time the selective impulscs arc being delivered by the subscriber. Thus the private magnet 103 is energized while the shaft is rotating and releases when the private magnet relay 101 dei nergizcs. allowing the side switch and side switch wipers 90 and 91 to pass to second position. The release relay 104 is operated by the line relay 100 in the first position of the side switch, and by the line relay 105 in the second position of the side switch. The said relay 104, when energized, opens the release magnet circuit, closes a portion of the rotary magnet circuit and puts a guarding potential on the first selector private bank contact corresponding to this switch to prevent its seizure by other selectors. The line relay 99 controls the ringer relay 106 and the ringer relay is also controlled by the rotating interrupter device The ringer relay 106, when energized, opens the circuit of the line relay 99, closes a path for the ringing current to pass through the wipers 88 and 89 to the line substations, and thus ring the bell tuned to this fre uency, and also connects the resistance 10 to one side of the line. The line'relay 99 must be considered marginal in its character. In other words, said relay will operatively energize with a receiver 03 the hook on the line with which it is in connection; but when one receiver only is ofl' the hook of a substation on said line, and the subscriber at said substation is pressing the button 10, said relay 99 will deenergize sufficiently to allow its armature to resume a normal position. Upon the switch shaft is mounted the arm 172 which, when the shaft is rotated one or more steps, permits the spring 109 to engage the contact point 110, whereby the release magnet 108 and the private magnet 103 are connected to the battery lead.

The operation of my connector switch may be more fully understood from an explanation of its operation when one partyline subscriber operates the central oflice switches to establish connection with another subscriber on the same line. It will be assumed that the subscriber at substation A, to which is allotted the number 1120, wishes to call the subscriber at substation A, to which is allotted the number 1320, according to the party-line system of numbering previously explained. It is assumed that the second level in the first selector banks is reserved for special use, as herein explained; in a oonsplcuous place on the telephone A is hung a placard giving the information that to call directory number 1320, call 25 and press the button; therefore the subscriber at substation A does not call substation A 1320 on his calling device, but by selecting the number 25 in the well known manner. When the receiver is removed from the hook the switch hook springs provide an energizing circuit for the line windings 27 and 28 of the line switch magnet 22, whereby the line switch C is operated to seizean idle and waiting or pre-selected trunk-line leading to a first selector switch D. The

by selecting the number .dial is turned for the first digit, and upon returning to normal position operates the first selector to establish connection with an idle trunk line on the second level leadin to a connector E. In a similar manner the impulses delivered by the dial for the last digit are directed toward the frequency connector E, which latter operates to place the shaft wipers in connection with the bank terminal contacts corresponding to the ringer generator of the pro er frequency for ringing the desired subscriliier The preliminary impulse for operating the line switch occurs when the receiver 2 is removed from the switch hook 3 and permits the spring 15 to engage the spring 16, thereby removing th ringer from across the line and bridging t e primary circuit instead. When the primary circuit is thus bridged across the line an energizing circuit is completed for the line relay windings 27 and 28, said circuit extending from ground G (F i 2) through the springs 111 and 112 of the master switch relay 55, through the line switch magnet springs 31 and 34, line conductor 115, through the primary circuit of the substation A to the line conductor 116, through the springs 33 and 35, thence through the line relay windin 27 and 28, master switch relay springs 117 and 118 to the batter lead 119, through battery to B ground The armature 29 is thereupon attracted, closing the springs 30 and 31 into contact, which closes a circuit through the trip winding 25, said circuit extending from ground G master switch relay springs 111 and 112, line switch springs 30 and 31, tri winding 25, through the line relay win ing 27, master switch relay springs 117 and 118 to the battery lead 119, thence through battery B to ound G. The energizing of the trip win mg 25 attracts both the plunger arm 18 and the armature 32 of the line switch magnet. The plunger (not shown), which is carried by the plunger arm, engages the line switch bank terminals of an idle and reselected trunk to a first selector switch 5, closing the bank springs 121 and 122, 123 and 124, 125 and 126 and 127 and 128 into contact, which extends the line conductors 115 and 116 through to the trunk conductors 129 and 130, thereby closing an energizing circuit through the double-wound line relay 79 of the selector D. The armature 32 of the line switch magnet 22, when attracted, breaks the contact points of the springs 33 and 35 and 31 and 34, thereby opening the circuit of the line relay winding 28 and clearing the line conductor 115 of the ground G All of the line switch armatures are now in an attracted position. The circuit throu h the double-wound line relay 79 may e traced as follows: from ground Gr through one winding of the double-wound line relay 79 to the contact point of the side switch, side switch wiper 60, trunk conductor 130, line switch bank springs 128'and 127, line conductor 115, through the rimary circuit of the substation A, line con uctor 116, bank springs 121 and 122, trunk conductor 129, side switch wiper 59, contact oint 64, through the other winding of the ins relay to the battery lead 119, thence, through battery B to ground G. The double-wound line relay 79 attracts its armature, closing an energizing circuit through the release relay 87. This circuit extends from ground G through the springs 131 and 132, through the release relay 87 to the battery lead 119, thence through battery B to ground G. The release relay in turn closes a circuit through the bridge-cut-ofi winding 26 of the line switch magnet 22. The winding 26, when energized, will hold the plunger arm 18 in an attracted position. The said circuit through this winding extends from ground G through the release relay springs 133 and 134,- private trunk conductor 135, bank sprin V 124 and 123, bridge-cut-oif winding 26 to the battery lead 119, thence through battery B to ground G. When the plunger presses the bank springs 125 and 126 into contact the master switch rotates all idle lungers that are in looking engagement with the plunger shaft 39 to a position opposite the next idle bank terminal similar to the terminal just engaged. This is accomglished in the following manner: When the ank springs 125 and 126 are in engagement a guarding potential is established on the master switch bank contact segment a individual to the trunk line seized. A circuit is thereby established through the auxiliary rela 52 as follows: from ground G through the ank springs 125 and 126, conductor 136 (Fig. 1) individual contact segment a, master switch wiper 41, common segment 42, auxiliary relay 52 to the battery lead 119, thence through battery B to ground G The auxiliary relay 52, when energized, closes an energizing circuit through the motor magnet relay 43 (Fig. 1), which circuit extends from ground G through the auxiliary relay springs 137 and 138, and the relay 43 to the battery lead 119, thence to battery B and ground G. The motor magnet relay now attracts its arn'iature, lifting the pin 46 out of locking engagement with the cam 44 and closing the springs 49 and 51 into engagement. The former action unlocks the shaft 39 and the latter closes a circuit through the relay 55 and the motor magnet 36 in multiple. The motor magnet circuit extends from ground Gr through the magnet winding 36, the interrupter springs 139 and 140, the motor relay springs 51 and 49 to the battery lead 119, thence to battery B and ground G. The motor magnet then operates to advance all idle plungers, as before exingthat IS,

plained. The circuit of the rela 55 extends rom ground Gr through said re ay, the motor magnet relay springs 51 and 49 to battery lead 119, thence through battery B to ground G. Said relay 55 is energized and carries the springs 117 and 112 out of engagement with the springs 118 and 111 and into engagement with the springs 141 and 142. This action destroys the main battery and ground connection with all the line switches in the group and makes connection with a busy signaling current. In this way any subscriber removing his receiver while the master switch is operating does not send the usual preliminary impulse to operate the line switch. Instead, if all the trunks are busy the master switch continues rotating and the subscriber will hear the busy signal. When this signal is out off he can proceed as usual. As long as the master switch wiper 41 continues to find a guarding potential on the next individual contact segments, the motor magnet will continue to advance the plunger shaft and plungers. However, when an idle trunk is found the relays 52 and 43 will be deenergized, and the pin 46 will drop into locking engagement with the cam 44, opening the contact between the springs 49 and 51 and the circuits of the motor magnet 36 and the relay 55.

The subscriber has now established connection with the next selector switch, which is now operated by the impulses that are delivered when the dial returns to normal osition for the first digit. 'The operation 0 the switches up to this point has occurred before the subscriber releases the dial for the first digit. The first digit being 2, the impulse spring 14 is twice carried out of engagement with the spring 13. As a result the energizing circuit through the line relay 79 is broken twice and the spring 131 comes into contact with the spring 43 twicxa. After the two impulses are thus transmitted the relay again energizes as before, closing the energizing circuit for the release relay 8 through the springs 131 and 132.' As previously ex lained, the relay 87 is slow-actslow to deenergize, and while this energizing circuit is momentarily broken during the vertical impulses just delivered, the said relay remains in an operated'position, with the contact closed. between the springs 144 and 145. In this way the vertical magnet is caused to energize twice, raising the shaft and shaft wipers to the second level of the contact banks. The energizing circuit of the "ertical magnet extends from ground Gr through the line relay rin 131 and 143, the release relay springs 144 and 145, the private magnet relay 80, the vertical magnet 81, contact point 66, side switch wiper 61 t0 the battery lead 119, through battery B to ground G. It will be seen that the private magnet relay 80 is ineluded in this circuit. The relay 80 also energizes, but being a slow-acting relay it remains energized until the impulses are transmitted. This relay 80 controls the private magnet 61 over the following circuit: from ground (1 through the private magnet relay springs 1-16 and 147, private magnet 64 to battery lead 119, thence through battery I to ground (l. The private magnet 6-1 accordingly operates when the relay 80 cnergizcs and dci ncrgizes and allows the side switch to pa s from first to second position, thus permitting the side switch wipers 61 and 02 to disengage the contact points 66 and (ET. and to engage the contact points 71 and 72. respectively. The closure of contact between the wiper 01 and the contact point Tl sets up an energizing circuit through the rotary magnet from ground (1 through the interrupter springs 148 and 14-), rotary magnet 82. contact point T1, wiper 61 to battery 11 and ground G. The said rotary magnet then operates to rotate the shaft and shaft wipers 50, 57 and 58 into engagement with the first contact of the second level of the sclcctor banks, from which banks it is assumed the trunk conductors lead to the connector la. 11' the first connector is busy the private magnet is energized over a circuit extending from ground G through anolncr switch (not shown) to the private bank contact, through the private wiper side switch wiper 62, contact point 72, private magnet 04 to the battery lead. thus locking the side switch in second position. The rotary magnet 82 will thus continue to rotate the shaft wipers until a trunk is found which is idle-that is, which has no guarding potential; then the privatc magnet will dei nergizc and permit tllc side switch to pass to third position and the side switch wipers to engage the thirdposition contacts. as shown in Fig. It is assumed, however, that the first connector is idle, in which case the side switch will he tripped to third position in the wellknown manner. 'hen the side switch wipers engage their third-posilion contacts the line. conductors 113 aml 1113 are extended over the conductors 1.30 and 15:3 to the connector 1). When the ulisci'llnil s line is thus ox (coded to the connector 1% an energizing circun is e tablished from ground (1" through the marginal relay $19, the ringer springs 151 and 15.3. conductor 15:2. trunk conductor I710, illlt' conductor 11.5, primary circuit of subtaeion A. line. conductor 110. trunk conduc l r 1:33 conductor 1.30. side so itch wiper 90, contact point 03.1ine relay 100 to the battery lead 119. thence through battery It to ground H. lloth relays included in this circuit are energized. The line relay 100 controls the relea e relay 101 in the same manner as in the .IliJl'l I l) liht described. The release r hi 101. when energized. establishes a zcirdmg poontial at the private bank con-- position, establishing a new tacts of other selectors to protect the connector E from being seized by another selector, and closes a new energizing circuit through the release relay 87 of the selector D from ground G through the release relay springs 155 and 156 of the connector E, trunk conductor 151, shaft wiper 58, side switch wiper 62, contact point 77 (since the side switch is in third position), release relay 87 to battery lead 119, thence through battery B to ground G. Said new energizing circuit prevents the selector D from releasing. The operation of the dial for the last digit affects the connector switch to rotate the shaft wipers 88 and 89 into connection with the bank contacts 5. When the dial is operated, the impulse spring 14 is five times carried out of engagement with the impulse spring 13, thereby momentarily deenergizing the line relays 09 and 100 five times, whereby the spring 157 engages the spring 158 five times, thus sending five impulses to the rotary magnet from ground G through the springs 1.37 and S. springs 159 and 160, private magnet relay 101, rotary magnet 102, contact point 94, side switch wiper 91 to the battery lead, thence through battery B to ground (1. The private magnet relay energizes when the first impulse is delivered, but being a slow-acting relay it remains in an operated position while the impulses are being delivered. The rotary magnet, upon being energized, operates one step at a time to carry the shaft and shaft wipers 88 and 89 into engagement with the bank contacts corresponding to the ringing current When the relay 101 operates an energizing circuit is established from ground G through the private magnet relay springs 1G1 and 162, the private magnet 103. otf-noruml spring 1011,, contact point 110 to the battery lead 110. thence through battery B to ground G. Of course. the normal spring 109 engages the contact point 110 as soon as the shaft is opcratcd one step. \Vhcn the relay 101 is decnergizod after all the impulses are delivcred. the private magnet is deiinergized and permits the side switch to take the second energizing circuit through the relay 105 from ground G through the marginal line relay 90, ringer relay springs 154 and 155, trunk conductor 15; and 1 10. line conductor 115, primary circuit of substation A, line conductor 116, trunk conductors 129 and 150, side switch wiper 00, contact point 96. relay 105 to the battery lead 119, thence through battery B to ground (11. Also, when the side switch wiper 01 engages the contact point 97 the ringer relay is closed to the battery lead 119. \Vhen the relay 105 operates, the spring 163 engages the spring 104, closing a new energizing circuit for the release relay 1th from ground tl'" through sprin s 103 and 104, rclcasc relay 101 to battery lead 119, thence through battery B to ground G, holding the release relay 10-1 in an operated position and thereby preventing a release of the switches (T, D and E as long as the relay 105 is energized. The marginal relay 99 is also in an operated position. holding the spring 165 out of engagement with the spring 166, thereby preventing the energization of the ringer relay. The subscriber will now press the button 10 in the well-known manner to ring the desired substation A thereb including the resistance 11 in series with t e primary circuit of the substation A. Thisadded resistance in the energizing circuit will not allow enough current to flow to sufiiciently energize the line relay 99; thus the armature of said relay resumes a normal position, shifting the spring 105 into engagement with the spring 160 to close an energizing circuit through the ringer relay 106 from ground G through the interrupter mechanism a, springs 165 and 166, ringer relay 106, contact point 97, side switch wiper 91 to the battery lead 119, thence through battery B to ground G. It will be seen that as the intcrriqiter mechanism revolves, the energizing circuit will be broken periodically, so as not to ring the called subscriber continuously. It will also be seen that each time the ringer relay is energized, the spring 155 is carried out of engagement with the spring 154 and into engagement with the springs 168 and 169, and also the spring 167 is carried into engagement with the spring 170, thereby bridging the terminals of the ringer generator i across the trunk conductors 150 and 152. It will also be seen that the line relay 99 is disconnected at the spring 155 and that the resistance 107 is connected to the spring 155 through the springs 108 and 109. Thus a new energizing circuit is provide for the line relay 105 from ground G through the resistance 107, ringer springs 168, 169 and 155, trunk conductors 152 and 130, line conductor 115, resistance coil 11, primary circuit of substation A, line conductor 116, trunkconductors 129 and 150, line relay 105 to battery lead 119, thence through battery ll to ground G. This circuit as traced from the ringer spring 168 to the trunk conductor 150, as previously traced, and to ringer springs 170 and 107 also atfords a path for the ringing current, but. in addition, ringing current is sent over the line to the other substation of this line. energizing the hell tuned to this ringing current, in this case the bell at substation A The ringer relay 100continues to energize intermittently each time that the interrupter a closes the circuit and the subscriber at substation A continues to press the button 10. llowever, as soon as the called subscriber answers. the line relay 99 is again opera tively energized, disconnecting the ringer relay from the ground interrupter. This energizing circuit extends over the same main line conductors as before, but extends farther to include in multiple with the resistance 11' and primary winding of the substation A the extended branch line conductors 115 and 110 in series with the primary circuit of the substation A This multiple circuit being of a relatively lower resistance allows sufficient current to flow to operativcl y energize the relay 99. The subscriber at substation A, not hearing the intermittent ringing buzz in his receiver, releases the button 10, thus short-cireuiting the resistance 11 and bridging his primary circuit directly across the line conductors in the same manner as substation A is now connected. The subscribers being thus connected may communicate over the branch line conductors 115 and 116, both drawing their talking battery current through the same line relays from the same source.

After the subscribers are through talking the last one to hang up his receiver initiates the release of all the switches by opening up the line circuit at the switch hook springs. This release is as follows: At the instant the circuit is broken at the switch hook springs, the line relays 99 and 105 are both dei nergized and the release relay 104 is deenergized by the line relay 105. At the instant the release relay 104 decnergizes the energizing circuit for the release magnet 108 is closed at the springs 171 and 160, the circuit extending from ground G through springs 157 and 158, springs 160 and 171, release magnet 108, spring 109,contact point 110 to the battery lead 119, thence through battery B to ground G. The release magnet 10S stantly releases the connector switch shaft. As soon as said shaft reaches its norma position it breaks the circuit for the release magnet 108 by separating the ofl' normal spring 109 fromthe contact point 110. The operation of the release relay not only causes the release of the connector E but also the release of the preceding switch I), because the ground connection from ground G to the trunk-release conductor is broken at the s ri s 155 and 156. Since the release relay 8 is r ependent upon this ground for its energized condition, as already explained, it will fall back and release the selector D in the same manner as explained for the connector. Furthermore, when the release relay 87 deiinergizes and separates the springs 133 and 134, the bridge-eut-ofl' windin of the line switch C is also det nergized, since the round G is disconnected and the line switch plunger arm 18 and armature 32 will resume a normal position, withdrawing the plunger 92 from the bank terminal.

it will be seen that I provide a two-wire antmnatic telephone exchange system in which there is a plurality of substations on a line, and means for enabling one subscriber to call others on the same line by providing special connector bank terminals equipped with current, and special connectors for connecting to said bank terminals, said connectors being reached by a special level at the selector banks, said level being designated for this special purpose. Said connectors and selector bank level are common to all subscribers in the system. However, said special level ma be designated at the first selector, secon selector or third selector, according to the size of the system and to original selection. I also rovide in common to all of the party hnes as many special numbers for ringing back on the calling line as there are substations on each line. It will also be seen that I provide means whereby, for selectively ringing another substation on the same line by pressing a push button, the called subscriber, upon answering, may cut ofi the ringing current and thus not be annoyed by a continuous ringing in the receiver until the calling subscriber releases the push-button.

From the foregoing it will be seen that the same connector may be employed for calling any one of several subscribers on the same line in a two-wire system. By a .two-wire system I mean a system in which the automatic switches are controlled over the two sides of the calling line in series. This connector, by reason of the frequency selectn-constitutes a. means for selectively si aling the subscribers on a party-line. l li e same connector is used regardless of the subscriber called, but different frequencies are employed for signaling the different subscribers, and the connector has allotted to it a frequency selector that enables the calling subscriber to select the frequency necessary for signaling a particular subscriber. This is the first instance so far as I now know, of the provision 0% means for calling back on the same line in a two-wire system. It is also the first instance, so far as I now know, of the provision of a frequency selector in a twowire system, whereby currents of different frequencies may be used for selectively signaling the subscribers on a party-line that is free from operati grounds at the substations thereon. 'l lle connector herein shown, such as the one at E, is not for extendin talking connections, but is employed for ma g connection with any one of several sources of ringing current. It is, therefore, in the nature 0 a frequency selector, inasmuch as it selects the desired frequency of ringing current and for that purpose is subject to control by the calling subscriber. Also, so far as I know, this is the first instance in which interrupted current has been sent back on the line to signal the called subscriber, in the manner described. By thus interrupting the current the calling subscriber is able to release. If the rin current was not so interrupted the line relay 105 would remain energized even after the calling subscriber hangs up the receiver. Furthermore, this intermittent flow of ringing current is necessary in order that the ringing current may be automatically disconnected from the line when the called subscriber answers. When the called subscriber answers, the relay 99 is energized to open the circuit of the ringer relay, as previously explained. Were it not for the interrupter d the relay 99 would remain disconnected from the line, and would therefore not be energized when the called subscriber answers. With the arrangement shown, the relay 99 is energized the first time it is momentarily connected with the line after the called subscriber answers. Thus, the interruption of the application of ringing current to the line, so that the ringin is intermittent, has a utility over and a ove that which it ordinarily has. It is old, of course, to use an intermittent flow of ringin current, so that the called subscribers bgl rings intermittently and not continuously. So far as I am aware, however, such method of intermittent ringing has not been taken advantage of to obtain the results which I have here described.

What I claim as my invention is 1. In a telephone system, a arty-line, a trunk, a ring-back apparatus ibr enabling one party to call another on the same line,

means for connecting the line with the said apparatus, and means for supplying differ ent kinds of ii current, said ring-back apparatus provided with means controlled by the calling party over the trunk for selecting the current necessary for si another party on the same line, and or projecting the selected current back to said line by Way of conductors in said trunk over which the selector is controlled to select the frequency.

2. In a telephone system, a party-line a trunk, a frequency selector apparatus ior enabling one party to call another on the same line, means includin a first selector for connecting the line with the said apparatus, and means for supplying currents of'difl'erent frequencies, said frequency selector apparatus provided with means controlled by the calling arty for selecting the frequency necessary or signaling another party on the same line, and means for proecting the selected current to said line by way of conductors in said selector over which the frequency selector is operated to select the proper quency.

3. In a telephone system a party-line, a trunk, means in said trunk for supplying difl'erent kinds of ringing current for selectively signalin on said line, and means controlled by a cal ing party on said line for connecting the line and the trunk and for operating said first means and for also pro- Lecting the selected current back to said line y way of conductors in said trunk over which the selector is controlled to select the frequency to si nal another party thereon.

4. In a telep one system, a party-line, conductors normally disconnected from the line, means associated with said conductors r and operated thereover for supplying ringing currents of diflerent frequencies for selective] si' aling on said line, and means control ed y a calling part on said line for connecting the desired requency with the line to signal another party thereon, and to project the same back to the line over the said conductors.

5. In a telephone system, a party-line, a frequency selecting apparatus for selectively signaling thereon, means for supplying ringing currents of different frequencies, a first selector for extending connection to said apparatus, means for extending connection from said line to said first selector, said frequency selectin apparatus provided with means controlled by the calling party for selecting the frequency necessary for signaling another party on the same line, and for projecting the same back to the line via said first selector.

6. In a telephone system, a party-line, and means for enabling one party to selectively signal the other parties on the same line, comprising means common to a plurality of such party lines controlled by the calling party over conductors normally disconnected from said line for selecting the proper signaling current necessary for signalmg another pgrty on the same line, and for projecting tsame back to the line via said conductors.

7. In a telephone system, a party-line, a selector adapted to operate in accordance with a di it of the called number when one arty cal s another on the same line, a ringack apparatus adapted to be selected and connected with the lineby said selector in response to the call, a circuit for controlling the sslectonsaid circuit including the two sides of! the line in series, means for supplying ringing currents of difierent frequencies,

and a circuit for controlling said ring-back apparatus to select the frequency necessary for eflibling one party to selectively si 9.] another party on the same line, said astmentloned circuit also including the two sides of the line in series. a

and mechanism for enabling the calling party to release said connection if the called party on the same line does not answer, said mechanism operative only during momentary interruption of the signaling current.

9. In a telephone system, a party-line, means for automatically extending connection from said line including a ring-back apparatus for enablin one party to call another on the same line, means for connecting the line with the said apparatus, and means for supplying different kinds of ringing current, said rmg-back apparatus rovided with means controlled by the cal ing party for selecting the current necessary for signaling another party on the same line, and provided with means for automatically projecting ringing current to the party line while the party line conductors are connected in series.

10. In a. telephone system, a lurality of party-lines and trunk lines ivided into groups, a ring-back apparatus for enabling one party to call another on the same line, a first selector having motion in one plane to select groups of trunks and motion in an intersectmg plane to find a trunk in a selected group for connecting the line with the said apparatus, said ring back having means for supplying currents of different frequencies to the calling line by way of said selector, said ring-back apparatus provided with means controlled by the calling party for selecting the frequency necessary for signaling another party on the same line.

11. In a telephone system, a party-line, means for enabling one party to selectively signal the other parties on the same line, comprising means for supplying difierent kinds of signaling current, means controlled by the calling party for selecting the current necessary for signaling another party on the same line, and automatic means for extending connection from said party-line, and for projecting ringing current to the party line automatically while the conductors are connected in series.

12. In a telephone system, a plurality of party lines, a talking circuit individual to each line over which subscribers at two telephones on a line may communicate, a signal for each telephone in each line, a source of signaling current and a switch for controlling the saluc. a trunk line common to said party lines, means for connectingany line with said trunk and for then operating said switch over said trunk and over two: sides of the talking circuit in series to apply said current to said line over the operating conductors to the trunk after the switch is operated for operating any one of said slgnals.

13. In a telephone system, a plurality of party lines, a talking circuit individual to each line over which subscribers at two telephones on a line may eornmiuiieate, a signal for each telephone in each line, a plurality of sources of signaling current; and a select: ing switch for selecting any one of said sources, a trunk line common to said party lines, means for connecting any line with said trunk and for then tilJtltllll'lg said switch over said trunk and over two sides of the talking circuit in series to apply said current to said line over the operating coir ductors of the trunk after the switch is operated for operating any one of said signals.

14. In a telephone system, a plurality of party lines, a talking circuit individual to each line over which subscribers at two telephones on a line may communicate, a signal of different character for each telephone in each line, a plurality of sources of signaling current and a selecting switch for selecting the particular one of said sources for operat ing the corresponding signal, a trunk linc common to said party lines, means for con necting any line with said trunk and for then operating said switch over said trunk and over two sides of the talking circuit in series to apply said current to said line over the operating conductors of the trunk after the switch is operated for operating any one of said signals.

15. In a telephone system, a plurality of party lines, a talking circuit individual to each line over which subscribers at two telephones on a line may communicate, a signal for each telephone in each line. a source of signaling current and a switch for controlling the same, a trunk line common to said party lines, means under the control of any telephone on any line for connecting" the corresponding line with said trunk and for then operating said switch over said trunk and over two sides of the talking circuit in series to apply said current to said line over the op eratmg conductors of the trunk after the switch is operated for operating a signal at another telephone on the same line.

16. In a telephone system, a plurality of party lines, a talking circuit individual to each line over which subscribers at two telephones on a line may communicate, a signal for each telephone in each line, a plurality of sources of signaling current and a selecting switch for selecting any one of said sources, a trunk line common to said party lines, means under the control of any telephone on any line for connecting the corresponding line with said trunk and for then operating said switch over said trunk and over two sides of the talking circuit in series to apply said current to said line over the operating conductors of the trunk after the switch is operated for operating a signal at another telephone on the same line.

17. In a telephone system, a plurality of party lines, a talking circuit individual to each line over which subscribers at two telephones on a line may communicate, a signal of a difi'ercnt character for each telephone in each line, a plurality of sources of signaling current and a selecting switch for selecting the particular one of said sources for operating the corresponding signal, a trunk line common to said party lines, means under the control of any telephone on any line for connecting the corresponding line with said trunk and for then operating said switch over said trunk and over two sides of the talking circuit in series to apply said current to said line over the operating conductors of the trunk after the switch is operated for operating a signal at another tele phone on the same line.

18, In a telephone system, a line, substations on said line, a plurality of ringing current generators at the exchange, means controlled by a calling subscriber over the two t-oruluctors otsaid line in series for selecting one of said generators and for connecting said line conductors to opposite poles thereof to signal a called subscriber, a battery, and means for substituting said battery for said generator thereafter to supply all the talking current to the calling and called substations.

19. In a telephone system, a line, substations on said line, a plurality of ringing current gene ators at the exchange, means controlled by a calling; subscriber over the two conductors of said line in series for selecting one of said generators and for connecting said line thereto to signal a called subscriber, a battery. and means controlled by the response of the called subscriber for disconnecting the selected generator and for connecting said battery in series with said line conductors to supply all the talking current to the calling and called substations.

20. In a telephone system, a party line, a plurality of ringing current generators at the exchange, means controlled by a calling subscriber on said line for selecting any one of said generators, means for connecting the selected generator to said line to signal it called subscriber thereon, means controlled by the calling subscriber over the two conductors of said line in series for actuating said connecting means, a battery, and means for thereafter connectiinc said battery in bridge of said line conductors to supply all the talking current to the calling and called substations.

21. A telephone exchange system including a party telephone line connecting a, plurality of party telephone line stations with an exchange, said telephone stations having signal receivers responsive to currents of differing character; selectii'ig mechanism at the exchange and operable by the equipment at any of said party telephone line stations, when calling, for extending said party tele phone line into connection with other telephone lines; a plurality of sources of signaling current for supplying the signal receivers at the aforesaid telephone stations with current to which said signal receivers are responsive; and means governed at any of said telephone stations, when calling, for causing said selecting mechanism selectivel to connect that one of said sources of signa ing current with said party telephone line which corresponds to the station upon said party telephone line that is to be signaled by the calling station upon the same line, said selecting mechanism serving to convey signaling current from the selected source to the selected party line station.

22. A telephone exchange system including a party telephone line connecting a plurality of party telephone line stations with an exchange, said telephone stations having signal receivers responsive to currents of differing character; selecting mechanism at the exchange and operable by the equipment at any of said party telephone line stations, when calling; a plurality of sources of signaling current for supplying the signal receivers at the aforesaid telephone stations with current to which said signal receivers are responsive; and means governed at any of said telephone stations, when calling, for causing said selecting mechanism selectively to connect that one of said sources of signaling current with said party telephone line which corresponds to the station upon said party telephone line that is to be signaled by the calling station upon the same line, said selecting mechanism servin to convey signaling current from the se ected source to the selected party line station.

23. In a telephone system, a line, a signal for said line, a. two-conductor trunk line, a switch for extending the line to the trunk line, means for releasing said switch, a source of current, means for connecting said source of current to the line over said trunk line to operate the signal, a relay for controlling said release means, said relay encrgized over the trunk line, another relay energized over the said trunk line for pre venting the said first relay from controlling said release means.

Signed by me at Chicago, Cook county, Illinois, this 26th da of November, 1909.

TA BOT G. MARTIN.

lVitnesses J. NORBY, SARAH Lnwrs. 

